JP2013-237327A and JP2014-234035A disclose an inverted pendulum vehicle comprising a vehicle body frame, a main wheel combining a plurality of free rollers arranged along a circle such that the rotational center lines of the free rollers are each directed along the tangential line of the circle, a pair of drive disks each carrying a plurality of free rollers configured to engage the free rollers of the main wheel, a pair of drive units including a pair of electric motors for individually driving the drive disks under an inverted pendulum control, a battery mounted on the vehicle body frame to supply electric power to the electric motors, and a saddle mounted on the vehicle body frame for seating a rider.
In the inverted pendulum vehicle disclosed in JP2013-237327A, the two drive units are positioned between the main wheel and the saddle in a vertically offset relationship relative to each other, and the battery is mounted on a rear end of the vehicle body frame.
In the inverted pendulum vehicle disclosed in JP2014-234035A, the two drive units are positioned between the main wheel and the saddle on either side of the vehicle body frame in a vertically aligned relationship, and the battery is mounted on a rear end of the vehicle body frame.
When the two drive units are vertically offset relative to each other as disclosed in JP2013-237327A, the lateral dimension of the vehicle can be reduced, but the vertical dimension of the part of the vehicle body frame occupied by the drive units is significant. Therefore, the saddle is required to be placed in a relatively high position so that the diameter of the main wheel has to be reduced for a rider of a short stature to be comfortably seated.
When the two drive units are vertically aligned to each other as disclosed in JP2014-234035A, the vertical dimension of the part of the vehicle body frame occupied by the drive units is reduced, but the lateral dimension of the vehicle has to be increased. Therefore, the legs of the rider have to be spread apart so that a rider of a short stature may not be comfortably seated.